Or HaChaim on Deuteronomy 18:14/אור החיים על דברים י״ח:י״ד

1 כי הגוים האלה..ישמעו, "For these nations..will hearken to, etc." This means that the Gentiles are forced to resort to astrologers and diviners who will tell them what the horoscope -forecasts; not so you, however. Forecasts based on horoscopes do not have the same meaning for you as they have for them as you have recourse to the prophets.

2The words לא כן, may also mean that you are not in a situation comparable to that of the Gentiles but G'd has made all the horoscopes subordinate to you. This is the meaning of Psalms 8,7 כל שתה תחת רגליו, "You have laid "the All" at his (Israel's) feet." [the verse commenced with "You have made him master over Your handiwork, (the universe) Ed.] Our sages in Shabbat 156 explain Isaiah 41,2: צדק יקראהו לרגלו, as referring to the planet Jupiter (the largest one) whom G'd has placed at the service of Abraham.

3נביא יקים לך, "G'd will make a prophet arise for you, etc." Finally, the Torah responds to the fact that the Gentiles appear better off having a chance to read the future, something apparently not granted to the Israelites. The Torah tells us that the function of the prophet includes telling us what is in store for us. Perhaps King Saul understood it thus when he asked the diviner to bring him in touch with the prophet Samuel (compare Samuel I 28,8). He thought that the prohibition to consult such people is applicable only when there were prophets who could be consulted instead. In the absence of such a prophet, Saul thought that it was legal to consult such people.